⚡ react-fast-context-z

LIVE EXAMPLE

Ultra-lightweight, selector-based state container for React. No Provider. No reducer. No proxy. No magic.

Designed to stay boring, explicit, and fast

Read and update state with the least possible runtime overhead.

Why react-fast-context-z?

• ⚡ Fast re-renders via fine-grained selectors
• ✍️ Explicit, imperative state mutation
• 🚫 No Provider / no Context tree
• 🧠 Framework-agnostic core (works outside React)
• 🔌 Clean integration with external logic / intent engines
• 📦 Tiny bundle, minimal runtime

Mental Model

intent / action
      ↓
 explicit mutation
      ↓
   state store
      ↓
 selector subscription
      ↓
 React re-render

No reducers.
No dependency graph.
No proxy tracking.

What you write is exactly what runs.

Installation

npm install react-fast-context-z

Basic Usage

import { createFastContext } from "react-fast-context-z"

const counter = createFastContext({
  state: { count: 0, loading: false },
  actions: {
    inc(s) {
      s.loading = true
      s.count++
      s.loading = false
    },
    add(s, n: number) {
      s.count += n
    },
  },
})

const double = counter.computed(s => s.count * 2)

export function Fast() {
  const count = counter.use(s => s.count)

  return (
    <>
      <div>{double.use()}</div>
      <button onClick={() => counter.actions.inc()}>
        {count}
      </button>
    </>
  )
}

Selectors & Derived State

Selectors subscribe only to what they read.

const double = counter.computed(s => s.count * 2)

function View() {
  const value = double.use()
  return <div>{value}</div>
}

• No re-render if selector output doesn’t change
• Derived selectors are memoized and reactive

Merge Mode

react-fast-context-z supports configurable merge strategies when updating state.

const store = createFastContext({
  state: { user: { name: "A", age: 20 } },
  merge: "shallow",
})

Available modes

merge: "shallow" (default)

• Shallow-merge object fields
• Mutated fields are preserved
• Ideal for mutable, intent-driven updates

set(s => {
  s.user.name = "B"
})
// keeps user.age

merge: "replace"

• Replace state reference entirely
• Useful when state is treated as immutable snapshots

set(() => ({
  user: { name: "B", age: 30 }
}))

When to use which?

| Mode | Use case | |------------|------------------------------------------------| | shallow | Explicit mutation, intent/actions, local state | | replace | Immutable data, server snapshots, undo/redo |

The merge mode is explicit — no hidden heuristics.

Batch & Transaction

Batch updates (single notify)

counter.batch(() => {
  counter.actions.inc()
  counter.actions.add(10)
})

Rollback-safe transaction

try {
  counter.transaction(() => {
    counter.actions.add(100)
    throw new Error("cancel")
  })
} catch {}

State is restored automatically if an error is thrown.

IntentX Integration

import { createIntentBus } from "intentx-core-z"
import { bindFastContext } from "react-fast-context-z"

const context = bindFastContext(counter)
const bus = createIntentBus(context)

bus.on("increment", ({ setState }) => {
  setState(s => {
    s.count++
  })
})

Designed to work cleanly with intent-first architectures.

Comparison

| Feature / Library | React Context | Redux | Zustand | Jotai | react-fast-context-z | | ---------------------------------- | ------------- | ----- | ------- | ----- | -------------------- | | Provider required | ⚠️ | ❌ | ❌ | ❌ | ❌ | | Selector-based render | ❌ | ✅ | ✅ | ✅ | ✅ | | Fine-grained updates | ❌ | ⚠️ | ⚠️ | ✅ | ✅ | | Proxy / atom graph | ❌ | ❌ | ❌ | ✅ | ❌ | | Reducers required | ❌ | ✅ | ❌ | ❌ | ❌ | | Direct mutation API | ❌ | ❌ | ⚠️² | ❌ | ✅ | | Works outside React | ❌ | ⚠️³ | ⚠️³ | ❌ | ✅ | | Intent / event-driven friendly | ❌ | ❌ | ⚠️ | ❌ | ✅ | | Async flow native | ❌ | ⚠️ | ❌ | ❌ | ✅ | | Devtools ecosystem | ❌ | ✅ | ⚠️ | ⚠️ | ❌ (by design) | | Bundle size | tiny | large | small | small | tiny |

Philosophy

• State should be boring
• Logic should be explicit
• Rendering should be fast

If you:

• already have a logic layer
• want full control over mutations
• hate hidden magic

Then this library is for you.

License

MIT